虛擬機上一臺主機，之前一直在用，可以通過xshell連接，但是忽然發現ping百度失敗了！

[root@mgt02 ~]# ping www.baidu.com
ping: unknown host www.baidu.com

檢查這個失敗感覺很麻煩，檢查了配置文件，修改了ip結果都不可以！但是發現ping ip地址是可以的！

[root@mgt02 ~]# ping 14.215.177.39             #百度的一個ip
PING 14.215.177.39 (14.215.177.39) 56(84) bytes of data.
64 bytes from 14.215
 
.177.39: icmp_seq=1 ttl=56 time=14.2 ms
64 bytes from 14.215.177.39: icmp_seq=2 ttl=56 time=5.94 ms
^C
--- 14.215.177.39 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1945ms
rtt min/avg/max/mdev = 5.941/10.113/14.285/4.172 ms
[root@mgt02 ~]

感覺應該是域名解析的問題，檢查了/etc/resolv.conf配置文件，發現文件是空的（不曉得為啥？）在文件中添加域名解析服務器！

[root@mgt02 ~]# cat /etc/resolv.conf 
nameserver 192.168.1.1              #當前服務器的網關
nameserver 8.8.8.8

問題解決：

[root@mgt02 ~]# ping www.baidu.com
PING www.baidu.com (14.215.177.39) 56(84) bytes of data.
64 bytes from 14.215.177.39: icmp_seq=1 ttl=56 time=13.0 ms
64 bytes from 14.215.177.39: icmp_seq=2 ttl=56
 
 time=6.62 ms
^C
--- www.baidu.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1732ms
rtt min/avg/max/mdev = 6.629/9.860/13.091/3.231 ms

記一次ping: unknown host錯誤